Gas recuperative flameless thermal oxidizer

ABSTRACT

The invention provides a gas recuperative flameless thermal oxidizer. The oxidizer includes a matrix bed and at least one feed passage extending at least partially within the matrix bed. The feed passage has an inlet configured to receive combustible vapor or an air-combustible vapor mixture and an outlet configured to deliver the combustible vapor or the air-combustible vapor mixture into the matrix bed. The feed passage has a cross-sectional area and a length within the matrix bed, wherein a ratio of the length (ft) to the cross-sectional area (in 2 ) is at least about 0.5:1.

FIELD OF THE INVENTION

This invention relates to a flameless thermal oxidizer. More particularly, this invention relates to a gas recuperative flameless thermal oxidizer and a method for oxidizing combustible vapor in a flameless thermal oxidizer.

BACKGROUND OF THE INVENTION

Many process streams of vapors, such as effluents from chemical processing plants, refineries, etc., utilize oxidizers to destroy the combustible vapor prior to release to the atmosphere. However, with increasing demands on the environmental control of emissions, the use of free flames to oxidize such effluents is in many cases unsatisfactory, since a free flame frequently results in incomplete combustion and uncontrollable production of undesirable side products, including for example carbon monoxide and nitrogen oxides. Thus, methods for destroying combustible streams to a high level of conversion with a minimum of pollutant production and in an energy-efficient manner are in continuing and increasing demand.

One example of a flameless thermal oxidizer is disclosed in U.S. Pat. No. 5,320,518, issued to Stilger et al, which is incorporated herein by reference. While the Stilger system represents an improvement over prior systems, there remains a need for improved flameless thermal oxidizers and methods for oxidizing combustible vapor in a flameless thermal oxidizer.

SUMMARY OF THE INVENTION

In one aspect, the invention provides a gas recuperative flameless thermal oxidizer. The oxidizer includes a matrix bed and at least one feed passage extending at least partially within the matrix bed. The feed passage has an inlet configured to receive combustible vapor or an air-combustible vapor mixture and an outlet configured to deliver the combustible vapor or the air-combustible vapor mixture into the matrix bed. The feed passage has a cross-sectional area and a length within the matrix bed, such that the ratio of the length (ft) to the cross-sectional area (in²) is at least about 0.5:1.

In another aspect, the invention provides a method of oxidizing combustible vapor in a gas recuperative flameless thermal oxidizer. The method includes delivering combustible vapor or an air-combustible vapor mixture into an inlet of a feed passage and through an outlet of the feed passage to a matrix bed below the lower flammability limit, while maintaining a length within the matrix bed of the feed passage such that a ratio of the length (ft) to the cross-sectional area (in²) is at least about 0.5:1.

In another aspect, the invention provides a gas recuperative flameless thermal oxidizer having at least one separate fuel inlet configured to introduce fuel into a matrix bed, the fuel inlet being positioned downstream of an outlet of a feed passage through which combustible vapor or an air-combustible vapor mixture is introduced into the matrix bed.

In another aspect, the invention provides a method of oxidizing combustible vapor by introducing fuel into a matrix bed through a separate fuel inlet at a position downstream of an outlet of a feed passage through which combustible vapor or an air-combustible vapor mixture is introduced into the matrix bed.

In another aspect, the invention provides a gas recuperative flameless thermal oxidizer, wherein a feed passage for combustible vapor or an air-combustible vapor mixture defines an interior extending within a matrix, the interior being substantially devoid of matrix.

In another aspect, the invention provides a method of oxidizing combustible vapor while maintaining an interior of a feed passage extending within a matrix substantially devoid of matrix.

In another aspect, the invention provides a gas recuperative flameless thermal oxidizer having a matrix bed positioned to exhaust gaseous oxidation products along an exhaust path, and at least one feed passage extending at least partially within the matrix bed. The feed passage has an inlet configured to receive combustible vapor and an outlet configured to deliver the combustible vapor into the matrix bed, the feed passage defining a combustible vapor path extending within the matrix in a direction substantially opposite that of the exhaust path of the matrix bed. The combustible vapor path of the feed passage and the exhaust path of the matrix bed are configured to provide a ratio between the velocity of combustible vapor in the combustible vapor path and the velocity of exhaust in the exhaust path between about 0.5:1 and about 1.5:1.

In another aspect, the invention provides a method of oxidizing combustible vapor by exhausting gaseous oxidation products along an exhaust path in the matrix bed in a direction that is substantially opposite that of the combustible vapor path of the feed passage. The method also includes maintaining a ratio between the velocity of combustible vapor in the combustible vapor path and the velocity of exhaust in the exhaust path between about 0.5:1 and about 1.5:1.

In another aspect, the invention provides a gas recuperative flameless thermal oxidizer having an enclosure, a matrix bed contained within the enclosure, feed tubes extending into the enclosure and at least partially within the matrix bed, and a matrix bed support mounted within the enclosure. The matrix bed support has a surface substantially impervious to the flow of exhaust supporting the matrix bed, the matrix bed support defining apertures each sized to receive a feed tube and exhaust passages proximal to the apertures.

In another aspect, the invention provides a method of oxidizing combustible vapor by directing substantially all gaseous oxidation products in a matrix bed through apertures in a matrix bed support adjacent feed tubes. The method also includes exhausting gaseous oxidation products from the gas recuperative flameless thermal oxidizer through an outlet in the enclosure.

In another aspect, the invention provides a gas recuperative flameless thermal oxidizer having an enclosure extending between opposed end portions, a matrix bed contained within the enclosure, feed tubes extending into the enclosure and at least partially within the matrix bed, and means for adjusting the distance between the opposed end portions of the enclosure to increase or decrease the size of the matrix bed.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a sectional side view of one exemplary embodiment of a flameless thermal oxidizer according to aspects of the invention.

FIG. 2 is a detail of one end of the flameless thermal oxidizer shown in FIG. 1.

FIG. 3 is a sectional side view of another exemplary embodiment of a flameless thermal oxidizer according to aspects of the invention.

FIG. 4 is a detail of one end of the flameless thermal oxidizer shown in FIG. 3.

FIG. 5 is a detail of the end of the flameless thermal oxidizer shown in FIG. 3 opposite from the end detailed in FIG. 4.

FIG. 6 is a detail of a fuel inlet in the end of the flameless thermal oxidizer detailed in FIG. 4.

FIG. 7 is a bottom view of an embodiment of a matrix support plate for use in the flameless thermal oxidizer shown in FIG. 3.

FIG. 8 is a top or bottom view of a tube sheet for use in the flameless thermal oxidizer shown in FIG. 3.

FIG. 9 is a schematic illustration of calculated isotherms in an exemplary embodiment of a flameless thermal oxidizer according to aspects of the invention.

DETAILED DESCRIPTION OF THE INVENTION

The invention will next be illustrated with reference to the Figures, wherein the same numbers indicate the same elements in all Figures. Such Figures are intended to be illustrative rather than limiting and are included herewith to facilitate explanation of the present invention. The Figures are not to scale, and are not intended to serve as engineering drawings. For simplicity, descriptions of the Figures will be based on an orientation of the flameless thermal oxidizer wherein the inlet and outlet nozzles are at the lower end of the unit when it stands upright. However, the unit may be operated in any orientation.

Generally, the present process and apparatus provide a method for controlling and stabilizing a flameless oxidation reaction wave in a heat-resistant solid matrix bed in which the combustible vapor is oxidized within a controlled area of the matrix at substantially uniform and relatively low temperatures, compared with temperatures produced in flames. The uniformity of the reaction wave, and the increased mixing and heat treatment afforded by the matrix, provide for a high conversion of reactants to products with a low level of production of undesired side products, including nitrogen oxides and carbon monoxide.

According to one exemplary embodiment, at least a portion of the bed is initially above the auto-ignition temperature of the mixture (typically a minimum temperature of about 1200° F.), whereby the mixture initiates an exothermic reaction in the bed, forming the reaction wave. This method and apparatus can be functionally applied to processes where the minimization of nitrogen oxides, ammonia, and products of incomplete combustion is desired in conjunction with either (a) destruction of a particular gas or vapor, or (b) combustion of fuel to generate heat.

Within an appropriate range of inlet mixture compositions, the reaction is substantially self-sustaining, i.e., little or no external heat is required to maintain the process temperature. The devices and methods provide unusually good recapture, or recuperation, of heat energy produced by the flameless thermal oxidation, resulting in the ability to efficiently oxidize input streams having relatively low fuel BTU content without the need to supply additional fuel to maintain the reaction, and to oxidize even lower BTU content streams by using only a relatively small amount of supplemental fuel.

More particularly, the present process and apparatus provides a method for flameless combustion in a reaction matrix of gases that have been preheated by an efficient recuperative heat exchange system. This provides a method for reducing the fuel concentration required for oxidation comprising, according to one embodiment, the steps of directing a mixture of the combustible vapor, with air and/or oxygen, into thermally conducting feed tubes embedded in a heat-resistant matrix bed, at least a portion of the bed initially being above approximately 1200° F., whereby the mixture oxidizes exothermally in the bed being premixed prior to entering, creating hot exhaust gases and heating the matrix. The matrix surrounding the feed tubes is heated by forced convection from the exhaust gases, as well as inner body thermal radiation and conduction in the matrix. The feed tubes are heated by thermal radiation from the surrounding matrix, as well as by conduction from the matrix and convection from the exhaust gases. Within an appropriate range of inlet mixture compositions, the reaction is substantially self-sustaining.

Referring generally to the exemplary embodiments selected for illustration in the Figures, the oxidizer 1, 100 includes a matrix bed 50, 150 and at least one feed passage 30, 130 extending at least partially within the matrix bed 50, 150. The feed passage 30, 130 has an inlet 56, 156 configured to receive combustible vapor or an air-combustible vapor mixture and an outlet 8, 108 configured to deliver the combustible vapor or the air-combustible vapor mixture into the matrix bed 50, 150. The feed passage 30, 130 has a cross-sectional area and a length L1 within the matrix bed 50, 150, wherein a ratio of the length L1 (ft) to the cross-sectional area (in²) is at least about 0.5:1. Typically, L1 is about 2 ft. or more. In use, combustible vapor or an air-combustible vapor mixture is delivered into the inlet 56, 156 of the feed passage 30, 130 and through the outlet 8, 108 of the feed passage 30, 130 to a matrix bed 50, 150 below the lower flammability limit, while maintaining a length L1 within the matrix bed 50, 150 of the feed passage 30, 130 such that a ratio of the length L1 (ft) to the cross-sectional area (in²) is at least about 0.5:1.

The gas recuperative flameless thermal oxidizer 1, 100 optionally has at least one separate fuel inlet 24, 124 configured to introduce fuel into the matrix bed 50, 150, the fuel inlet 24, 124 being positioned downstream of the outlet 8, 108 of the feed passage 30, 130 through which combustible vapor or an air-combustible vapor mixture is introduced into the matrix bed 50, 150. In one embodiment, the fuel inlet 24, 124 is proximal to the outlet 8, 108. In use, fuel is introduced into the matrix bed 50, 150 through the separate fuel inlet 24, 124 at a position proximal to the outlet 8, 108 of the feed passage 30, 130 through which combustible vapor or an air-combustible vapor mixture is introduced into the matrix bed 50, 150.

The feed passage 30, 130 of the gas recuperative flameless thermal oxidizer 1, 100 defines an interior extending within a matrix, the interior optionally being substantially devoid of matrix. In use, combustible vapor is oxidized while maintaining the interior of the feed passage 30, 130 substantially devoid of matrix.

The matrix bed 50, 150 of the gas recuperative flameless thermal oxidizer 1, 100 is positioned to exhaust gaseous oxidation products along an exhaust path, and the feed passage 30, 130 defines a combustible vapor path extending within the matrix in a direction substantially opposite that of the exhaust path of the matrix bed 50, 150. The combustible vapor path of the feed passage 30, 130 and the exhaust path of the matrix bed 50, 150 are optionally configured to provide a ratio between the velocity of combustible vapor in the combustible vapor path and the velocity of exhaust in the exhaust path between about 0.5:1 and about 1.5:1. In use, gaseous oxidation products are exhausted along the exhaust path in the matrix bed 50, 150 in a direction that is substantially opposite that of the combustible vapor path of the feed passage 30, 130, while maintaining a ratio between the velocity of combustible vapor in the combustible vapor path and the velocity of exhaust in the exhaust path between about 0.5:1 and about 1.5:1.

The gas recuperative flameless thermal oxidizer 1, 100 has an enclosure 2, 102, a matrix bed 50, 150 contained within the enclosure 2, 102, feed tubes 31, 131 extending into the enclosure 2, 102 and at least partially within the matrix bed 50, 150, and a matrix bed support 117 mounted within the enclosure 2, 102. The matrix bed support 117 optionally has a surface substantially impervious to the flow of exhaust supporting the matrix bed 50, 150, and the matrix bed support 117 defines apertures 127 each sized to receive a feed tube 31, 131 and to define exhaust passages proximal to the apertures 127. In use, substantially all gaseous oxidation products in a matrix bed 50, 150 are directed through apertures 127 in the matrix bed support 117 adjacent feed tubes 31, 131, and gaseous oxidation products are exhausted from the gas recuperative flameless thermal oxidizer through an outlet 20, 120 in the enclosure 2, 102.

The gas recuperative flameless thermal oxidizer 1, 100 has an enclosure 2, 102 extending between opposed end portions 103 a, 103 b, a matrix bed 50, 150 contained within the enclosure 2, 102, feed tubes 31, 131 extending into the enclosure 2, 102 and at least partially within the matrix bed 50, 150, and optional means for adjusting the distance between the opposed end portions 103 a, 103 b of the enclosure 2, 102 to increase or decrease the size of the matrix bed 50, 150.

Referring specifically to the several embodiments selected for illustration, FIG. 1 shows an exemplary embodiment of a flameless thermal oxidizer according to aspects of the invention, indicated generally at 1. The oxidizer 1 comprises a shell 2 enclosing a matrix bed 50, through which pass one or more feed tubes 31 that define one or more feed passages 30. The feed tubes 31 are connected to a source of combustible vapor (not shown) at an inlet nozzle 10, by way of a combustible vapor plenum 7, providing combustible vapor flow 25 into the feed tubes 31 at inlets 56 and along the feed passages 30.

The feed tubes 31 may contain a matrix, which may be the same as or different from that used in matrix bed 50. A description of suitable matrix materials is presented later herein.

In one embodiment, at least the section of feed tube 31 that lies within matrix bed 50 is essentially devoid of matrix. By using such an arrangement, heat transfer between the combustible vapor and the exhaust gases is improved, thereby improving the thermal efficiency of the unit.

More specifically, it has been discovered that the lack of matrix within the feed passages improves performance by enhancing heat transfer rates from the interior walls of the feed tubes that define the feed passages. While it is recognized that matrix material is optionally provided within the feed tubes, a lack of matrix in the feed passages was discovered to increase the gas velocities at the wall and to minimize the stagnant film thickness. In practice, the matrix actually obstructed the path for radiant heat transfer at the tube walls, and repeated heating/cooling cycles caused the matrix to crush. This crushing changes the fluid dynamic properties of the system and can cause the system to become non-uniform resulting in misdistribution of hot gases. When such an imbalance is permitted to progress, performance may suffer because some tubes may have essentially little flow with no effective heat transfer and others may have large flows with reduced heat transfer and short residence times. The lack of matrix may, therefore, in at least some cases, increase gas residence time in the tubes, remove obstructions to radiant heat transfer, and provide a balanced gas flow pattern. It is believed that this will result in improved performance by enhancing heat transfer rates from the interior feed tube walls.

Combustible vapor exits the feed tubes 31 and travels through matrix bed 50, during which time the combustible vapor is oxidized to a high level of completion to form gases constituting an exhaust flow, indicated at arrows 26, the flow of which is in a direction essentially opposite that of combustible vapor flow 25. The exhaust gases enter an exhaust plenum 9 and exit the flameless thermal oxidizer via an outlet nozzle 20.

An optional fuel plenum 12, fed by a fuel supply port 14, is situated at the end of the flameless thermal oxidizer opposite the end where the inlet nozzle 10 is located. Fuel is delivered to fuel supply port 14 from a source (not shown) of supplemental fuel. While a variety of fuels are contemplated, exemplary fuels may comprise natural gas, propane, No. 2 fuel oil, or any combustible petroleum-based fuel. Details of the upper end portion of the oxidizer illustrated in FIG. 1 are shown in FIG. 2.

FIG. 2 shows the end of flameless thermal oxidizer 1 comprising the fuel plenum 12. Exiting combustible vapor 29 issues from outlets 8 formed in the feed tubes 31. In one embodiment of the invention, fuel is supplied via fuel plenum 12 and flows in direction 37 through a series of fuel inlets 24, each of the fuel inlets 24 creating a mixing region 28 where fuel and exiting combustible vapor from respective outlets 8 mix together. A single inlet as opposed to plural fuel inlets 24 may also be used, which may confer certain advantages in terms of simplicity of construction of the device. More typically, multiple inlets, although not necessarily of the same number as the outlets 8, will be used in order to increase the homogeneity of mixing of fuel with the incoming combustible vapor. In one embodiment, each fuel inlet 24 is positioned proximal to an outlet 8 of a feed tube 31.

FIG. 3 shows another exemplary embodiment of a flameless thermal oxidizer according to aspects of the invention, indicated generally at 100. The oxidizer comprises a shell 102 enclosing a matrix bed 150, through which pass one or more feed tubes 131 that define one or more feed passages 130. For clarity, only two feed tubes 131 are illustrated in FIG. 3. A variety of quantities of feed tubes 131 and feed tube configurations (such as that shown in FIG. 7, described later) can be used depending upon the particular conditions in which the oxidizer will be used.

The feed tubes 131 are connected to a source of combustible vapor (not shown) at inlet nozzle 110, by way of combustible vapor plenum 107, providing combustible vapor flow 125 into the feed tubes 131 and along the feed passages 130 (upwardly in the embodiment illustrated in FIG. 3, though other horizontal or angled orientations are contemplated as well). Combustible vapor exits the feed tubes 131 at respective feed passage outlets 108 and travels through matrix bed 150, during which time the combustible vapor is oxidized to form exhaust gases, which enter an exhaust plenum 109 and exit the flameless thermal oxidizer 100 at an outlet nozzle 120.

An optional fuel plenum 112, fed by a fuel supply port 114 and a fuel source (not shown), is situated at the upper end of the flameless thermal oxidizer. In the embodiment shown in FIG. 3, fuel is supplied via fuel plenum 112 through fuel inlets 124 into matrix bed 150. Although a fuel plenum is shown in FIG. 3, it is not required; fuel may be passed directly to the fuel inlets by other means, for example dedicated individual conduits. Similarly, an exhaust plenum is not required.

The fuel plenum 112 is defined by an upper head 103 a of the oxidizer 100 as well as a plate 116 that separates the fuel plenum 112 from an interior region of the oxidizer 100 that contains the matrix bed 150. Similarly, the combustible vapor plenum 107 is at least partially defined by a lower head 103 b and a tube sheet 106.

As is illustrated in FIG. 4 and FIG. 5, the fuel inlets 124 pass through the plate 116 and insulation or refractory 151, which separate the upper head 103 a from the rest of the flameless thermal oxidizer 100. One or more (typically four) optional thermowells 115 pass through upper head 103 a and the plate 116, providing access ports for temperature measuring probes that may optionally be used in the flameless thermal oxidizer 100 to monitor temperature at various locations therein. Upper head 103 a may be attached to the shell 102 with flanges 104, which are also used to connect other sections of the flameless thermal oxidizer 100.

In the embodiment shown in FIG. 3, an optional wall section such as wall section 160 is used to lengthen the flameless thermal oxidizer 100. In other words, if in a particular application it is desired to increase the length of the oxidizer 100 (i.e., the length between heads 103 a and 103 b in the embodiment illustrated in FIG. 3), a wall section such as wall section 160 can be coupled between other wall sections or between a wall section and a head of the oxidizer. Such coupling can be accomplished using conventional flange and gasket systems, for example. Similarly, if in a particular application it is desired to decrease the length of the oxidizer 100, a wall section such as wall section 160 can be removed from between other wall sections or from between a wall section and a head of the oxidizer. This ability to lengthen or shorten the oxidizer enclosure makes it possible to lengthen or shorten the exhaust path of combusted vapor as it passes through the matrix bed.

Corresponding couplings 132 are used to couple one or more extension sections within feed tubes 131, e.g., to lengthen or shorten feed tubes 131 in a manner corresponding to the lengthening or shortening of the oxidizer 100. In other words, if in a particular application it is desired to increase the length of the feed tubes 131 (i.e., the length between inlet 156 and outlet 108 in the embodiment illustrated in FIGS. 3-8), a tube section can be coupled between other tube sections or between a tube section and an end portion of the matrix bed. Such coupling can be accomplished using conventional coupling systems, for example. Similarly, if in a particular application it is desired to decrease the length of the feed tubes 131, a tube section can be removed from between other tube sections or from between a tube section and an end portion of the matrix bed. This ability to lengthen or shorten the feed tubes makes it possible to lengthen or shorten the path of combustible vapor as it passes through the feed tubes.

Optional sampling nozzles are shown at 105. Such nozzles 105 provide access from an exterior of the oxidizer 100 to the matrix bed 150 for sampling the matrix at various locations in the oxidizer or for other purposes.

Feed tubes 131 and matrix bed 150 have diameters D1 and D2, respectively, with feed tubes 131 having a length L1 within the matrix bed 150. The interior of flameless thermal oxidizer 100 has a length L2, defined between the matrix support plate 117 at the bottom portion of the oxidizer 100 and the bottom surface of the insulation 151 at the top portion of the oxidizer 100. The matrix bed 150 is contained within shell 102 at one end by the matrix support plate 117, which may be structurally reinforced with the support bars 118 illustrated in FIGS. 3, 5, and 7.

The feed tubes 131 pass through matrix support plate 117 at the base of the matrix bed 150 and through tube sheet 106, which tube sheet 106 forms a seal against the feed tubes and thereby separates exhaust plenum 109 from combustible vapor plenum 107. Lower head 103 b forms the bottom of exhaust plenum 109, which may optionally include a preheat burner mounting nozzle 119. End portions of the feed tubes 131 extend into the combustible vapor plenum 107 to receive combustible vapors.

FIGS. 4 and 5 are details of the upper and lower ends, respectively, of the flameless thermal oxidizer 100 shown in FIG. 3. FIG. 5 shows pipe caps 155 connected to bottom ends of the feed tubes 131 with inlet holes 156 through them, to restrict the size of the inlet opening through which combustible vapors enter the feed tubes 131. More specifically, the size of the inlet holes 156 formed in the pipe caps 155 on the ends of feed tubes 131, which project into combustible vapor plenum 107, controls the characteristics of the flow of vapors as they enter the feed tubes 131. Smaller or larger openings 156 can be provided, or pipe caps 155 can be eliminated, depending upon the operational parameters of the system and system requirements.

FIG. 6 is a detail of the upper section of the flameless thermal oxidizer 100 shown in FIG. 4, showing fuel inlets 124 each comprising a pipe 152 having a cap 153 with a hole 154 through it, with the inlet passing through plate 116 and insulation 151. More specifically, and similar to the inlet holes 156 formed in the pipe caps on the bottom ends of the feed tubes 131, the size of the holes 154 formed in the pipe caps 153 on the ends of fuel inlet pipes 152, which project outwardly from the fuel plenum 112, controls the characteristics of the flow of fuel as it exits the pipes 152. Smaller or larger holes 154 can be provided, or pipe caps 153 can optionally be eliminated.

FIG. 7 is a bottom view from the underside of matrix support plate 117, according to one embodiment of the invention, schematically showing a plurality of feed tubes 131 having an outer diameter D1 passing through apertures 127, having a diameter D4, in the plate 117. The matrix support plate 117 is supported by optional support bars 118, and has an overall diameter D3 selected to correspond to the diameter of the oxidizer's shell 102. The matrix support plate 117 is dimensioned and selected from materials sufficient to support matrix in matrix bed 150 and delineate the matrix bed 150 from the exhaust plenum 109.

A pitch P (FIG. 7) is defined by the inter-axial distance between adjacent feed tubes 131. An appropriate pitch P is selected based on the diameter and length of the matrix bed 150, the diameter D1 or shape of the feed tubes 131, the number of feed tubes 131, the pattern in which the feed tubes 131 are positioned, and other aspects of the oxidizer design.

Changing the pitch P will change the flow characteristics of exhaust gases through the matrix bed. For example, increasing the pitch P between feed tubes 131 having a particular diameter D1 will increase the size of the spaces in the matrix bed 150 through which exhaust gases will flow. Conversely, decreasing the pitch P between feed tubes 131 having a particular diameter D1 will reduce the size of the spaces in the matrix bed 150 through which exhaust gases will flow. Similarly, increasing or decreasing the pitch P will also impact the heat transfer characteristics of the oxidizer. More specifically, a change in pitch P will change the characteristics of heat transfer from the exhaust gases in the matrix bed 150 to the combustible vapors in the feed tubes 131. Typically the pitch will be between one and eight inches, more typically between five and eight inches.

While a variety of combinations of dimensions can be selected, the embodiment of the oxidizer 100 selected for illustration in the Figures includes feed tubes 131 having a diameter D1 of about 3.5 inches, for example, and a pitch P of about 5 inches, for example. Accordingly, the clearance for exhaust gases flowing between adjacent feed tubes 131 is about 1.5 inches. Other dimensions can be selected based on design considerations, and this invention is not limited to any such dimensions.

The apertures 127 formed in the matrix support plate 117 are substantially open around the perimeter of the feed tubes 131, thereby allowing passage of exhaust gases out of the matrix bed into the exhaust plenum. More specifically, the gap defined between the diameter D4 of the apertures 127 and the outer diameter D1 of the feed tubes 131 provides a passage for the flow of exhaust gases from the matrix bed 150 to the exhaust plenum 109. For example, in an embodiment having feed tubes 131 with a diameter D1 of 3.5 inches and apertures having a diameter D4 of 3.5625 in., an annular gap of 0.03125 in. is provided for the flow of exhaust gases.

While many diameters D1 and D4 can be selected, the resulting gap is preferably small enough to avoid the passage of matrix materials from the matrix bed 150 into the exhaust plenum 109. Also, for reasons explained in greater detail later, the support 117 is optionally substantially impervious to exhaust gas flow in order to direct all exhaust flow toward the annular gap formed between apertures 127 and the outer surfaces of the feed tubes 131. Briefly, such direction of exhaust gases against or adjacent the outer surfaces of the feed tubes 131 helps to equalize the distribution of exhaust gases as it passes from the matrix bed 150 into the exhaust plenum 109 (as opposed to a concentration of exhaust gases exiting the matrix bed 150 into the exhaust plenum 109 at a position proximal to the exhaust outlet 120). This equalization tends to provide a more even and desirable temperature profile throughout the matrix bed. The direction of exhaust gases against or adjacent the outer surfaces of the feed tubes 131 also helps to optimize and equalize the transfer of heat from the exhaust gases to the combustible vapors in the feed tubes 131.

Though the apertures 127 in matrix bed support 117 illustrated in FIG. 7 are round, they may be of any shape depending on factors such as the shape of the feed tubes 131, the desired fit between the feed tubes 131 and the apertures 127, and the pattern of flow of exhaust gases desired through the apertures 127. For example, the apertures 127 can have an inner portion corresponding to the outer shape of the feed tubes 131 (whether round, square, or any other geometric shape) with contours extending outwardly from that inner portion to provide exhaust passages. Accordingly, star-shaped apertures, apertures with outwardly extending slots, elliptical, non-round, and other shapes are contemplated for apertures 127.

FIG. 8 is a top or bottom view of the tube sheet 106, which defines a boundary between the combustible vapor plenum 107 and the exhaust gas plenum 109. In the embodiment of the tube sheet 106 shown in FIG. 8, holes of diameter D1 are formed in the tube sheet 106, through which feed tubes 131 (not shown) are positioned. The feed tubes 131, which are sealed to the tube sheet 106 to inhibit the passage of exhaust gases from the exhaust plenum into the combustible vapor plenum, are optionally welded to the tube sheet 106, press fit into the tube sheet 106, or are otherwise positioned to reduce or prevent the escape of exhaust gases. Though the holes in tube sheet 106 illustrated in FIG. 8 are round, they may be of any shape depending on the shape of the feed tubes 131 and the desired fit between the feed tubes 131 and the holes.

In the embodiment shown, the tube sheet 106 has a diameter D3 equal to that of the diameter of matrix support plate 117, but this is not required. The diameter of the tube sheet 106 can also be larger or smaller than the diameter of the matrix support plate 117.

Returning again to FIG. 1, the materials of construction of flameless thermal oxidizer 100 are chosen to be capable of withstanding the reaction conditions and containing the process streams during operation. Typically, the shell and feed tubes are constructed of a metal such as carbon steel, Haynes Alloy HR-160, Haynes Alloy No. 214, Inconel Alloy No. 600, Inconel Alloy No. 601, or Stainless Steel Nos. 309, 310 and 316. Typically, the shell is constructed of carbon steel, and the feed tubes are constructed of two or more metals welded together such as carbon steel and stainless steel (such as Stainless Steel No. 310). Though the foregoing materials are discussed for purposes of illustration, it is contemplated that the oxidizer 100 can be formed from any metallic or non-metallic material.

The shell of the oxidizer 100 and the feed tubes 131 are typically cylindrical in shape, but they may be of any cross-sectional shape and size. Also, although the feed tubes 131 are shown to be substantially straight and substantially parallel to one another, one or more of the feed tubes 131 can be curved or oriented at an angle with respect to other tubes or the shell of the oxidizer.

The interior or exterior surfaces of the shell may be lined with one or more refractory insulating materials. Typically, the interior surfaces of the shell are lined with one or more refractory materials so that the shell does not have to be constructed of more expensive heat resistant metals. The refractory materials may be for example firebrick, optionally coated with a porosity-reducing compound, ceramic fiber board, or ceramic fiber blanket, or combinations thereof. In one embodiment, the shell is lined with dense castable refractory materials and backed up with insulating refractory materials, such as a ceramic fiber board and a ceramic fiber blanket. The shell surfaces may also optionally be coated with a non-permeable, corrosion-resistant coating, such as is known in the art.

The matrix bed contains heat resistant inert porous media. Typical materials used to construct the matrix bed are ceramic materials, which may be randomly packed or structurally packed. Random packing comprises ceramic balls that may be layered. Generally, for oxidation of organometallic compounds, nitrogen-containing compounds, sulfonated compounds, non-halogenated and halogenated hydrocarbon gases, the ceramic balls are useful if they have a diameter from about 0.0625 to 3 inches (0.159-7.62 cm), typically about 0.75 inch (1.9 cm). Another useful configuration is the use of random ceramic saddles typically from 0.0625 to 3 inches (0.159-7.62 cm) nominal size, typically about 0.5 to 1.5 inches (1.27-3.81 cm) nominal size. Other useful packing materials are pall rings and raschig rings with diameters from about 0.0625 to 3 inches (0.159-7.62 cm), and typically from about 0.5 to 1.5 inches (1.27-3.81 cm). Other ceramic materials may be utilized in the shape of a honeycomb or dogbones.

A ceramic foam material may also be used to construct the matrix bed. Typical foam material that can be utilized has a void fraction of 10 to 99%, typically 65 to 95%, and most typically about 70%. The pore sizes in any preferred ceramic foam material will be about 0.1 to 1,000 pores per inch (about 0.04 to 400 pores per cm), typically about 1 to 100 pores per inch (about 0.4 to 40 pores per cm), and most typically about 10 to 30 pores per inch (about 4 to 12 pores per cm).

Instead of a ceramic, the heat-resistant material used to form the matrix bed may also be a metal, which may be randomly packed or may have a structured packing. A pre-designed, single piece metal structure can also be used to constitute the matrix bed, which structure can be secured to the shell and thereby easily removed for maintenance purposes. Catalytic materials may be used in the matrix bed to promote oxidation or other desired reactions, but typically the materials that constitute the matrix bed are non-catalytic.

Generally, the void fraction of the matrix bed will be between 0.3 and 0.9. In addition, the material in the matrix bed will typically have a specific surface area ranging from 40 m²/m³ to 1040 m²/m³.

Returning again to FIG. 2, according to one embodiment of the invention, a supplemental fuel is optionally introduced into the flameless thermal oxidizer through fuel supply port 14 into fuel plenum 12, flowing in direction 37 through fuel inlets 24, creating a mixing region 28 where fuel and exiting combustible vapor mix together. In one embodiment of the invention, the fuel inlets 24 are situated directly above some or all of the feed tubes 31, such that the flows of combustible vapor and fuel impinge upon each other. However, it is not required that the fuel inlets be so situated, and they may for example be displaced from co-linearity with the axes of the feed tubes. Typically, the length of the matrix bed will be such as to bring it approximately even with the end of feed tubes 31, but the matrix bed may terminate either above or below that point (with reference to the orientation shown in FIG. 2).

Returning again to FIG. 3, one or more optional thermowells 115 pass through upper head 103 a, providing access ports for temperature measuring probes that may optionally be used in the flameless thermal oxidizer to help control the reaction wave shape and monitor temperature at various locations therein. The operation of such probes may help to ensure that the system is working at proper temperature and flow conditions in order to achieve efficient oxidation of combustible vapor and (optionally) fuel. Upper head 103 a may be attached to shell 102 with flanges 104, which are also used to connect other sections of the flameless thermal oxidizer 100. However, other methods of attachment may be used, and any of the various parts of the flameless thermal oxidizer 100 may be integrated into a unitary piece, without joints or flanges. Optional sampling nozzles 105 are used to remove samples of gases at various locations in the flameless thermal oxidizer 100, for example for analytical purposes to verify that oxidation is proceeding to a high level of completion.

In the embodiment shown in FIG. 3, an optional wall section 160 is used to lengthen the flameless thermal oxidizer. Corresponding couplings 132 are used to extend feed tubes 131 accordingly. Such sections of wall and feed tube may be of any length, and two or more such sections may be arranged in series to achieve a desired length.

Feed tubes 131 may have any ratio of length to cross sectional passage area. In some exemplary embodiments of the invention, the ratio of length in feet within the matrix bed to the cross sectional area in square inches of each of the feed passages 130 defined by the feed tubes 131 is at least about 0.5:1. A ratio less than about 0.5:1 may compromise the heat transfer benefits achieved according to aspects of this invention. A ratio of at least about 1.2:1 is typical. Also, the ratio of length in feet within the matrix bed to the cross sectional area in square inches of each of the feed passages 130 defined by the feed tubes 131 is typically less than about 2.5:1. A ratio above about 2.5:1 may increase the pressure drop of gas flowing through the feed passages 130. Typically, therefore, a range of the length:area ratio may be maintained between about 0.5:1 and about 2.5:1. More typically, a range of the length:area ratio may be maintained between about 1.2:1 and about 2.1:1. In some embodiments of the invention, the ratio is about 1.6:1.

Flameless thermal oxidizers having length to cross sectional area ratios within these ranges may provide an especially good balance between good thermal transfer from the exhaust gas to the combustible vapor and sufficient flow rate at convenient back-pressure levels. In one embodiment of the invention, the cross sectional area of an individual feed passage 130 is typically about 7.4 in². In another embodiment, the length of the portion of feed passage within the matrix bed is about 12 feet or more.

The total cross sectional area defined by the one or more feed passages 130, taken together, may be of any percentage relative to the cross sectional area of the matrix bed, calculated from D2. Typically, the percentage will be between about 10% and 50%. More typically, the percentage will be between about 20% and 30%.

In operation, a preheat burner (not shown) may be attached to the flameless thermal oxidizer at mounting nozzle 119, to provide heat to the system during startup. Typically, the burner will be shut off once the flameless thermal oxidizer 100 has reached operating temperature, which is typically substantially or completely self-sustaining. The burner may operate on any type of fuel, and may for example use the same fuel as is supplied to fuel inlets 124, for example natural gas. Alternatively, an electrical heater or other heat source may be used.

Returning again to FIG. 6, fuel inlet 124 may be constructed as shown from a piece of tube or pipe 152, and terminated with a cap 153 having in it a hole 154. Any of a number of other configurations of fuel inlet 124 may be used, provided that they allow the introduction of a fuel into the flameless thermal oxidizer 100. Preferably, fuel inlets 124 are positioned to allow the introduction of a fuel into the flameless thermal oxidizer 100 proximal to the end openings 108 of feed tubes 131. The inlets 124 may for example be simple gas jets, or they may be spray heads for use with relatively nonvolatile fuels, for example No. 2 fuel oil.

Returning again to FIG. 7, one embodiment of matrix support plate 117 is shown from the side of the exhaust plenum 109 (i.e., from the bottom), with feed tubes 131 passing through apertures 127 in the plate. The apertures shown in the embodiment of FIG. 7 are circular, but they may be of any shape. They are of a size sufficient to allow escape of exhaust gases from the matrix bed, along the feed tubes 131, and into the exhaust plenum. It is preferred that the apertures 127 provide some degree of resistance to exhaust gas flow; this tends to improve uniformity of gas flow across the matrix bed, resulting in a better-controlled thermal oxidation and greater thermal efficiency.

Although the diameter D4 of the apertures 127 is shown in FIG. 7 as substantially constant at all locations, the diameters may be varied, for example to compensate for wall effects or other causes of non-homogeneity in the exhaust gas flow. The embodiment shown in FIG. 7 shows the feed tubes 131 arranged in a triangular packing arrangement, defined by a pitch P. However, other packing arrangements, for example square, may be used.

The relationship between tube pitch, tube diameter, and matrix bed diameter controls heat transfer and fluid dynamic characteristics. Overall thermal efficiency and organic destruction efficiency is governed by these parameters. Heat transfer rates are affected by, inter alia, fluid velocities, line of sight radiant heat transfer, turbulence, and thermal conductivity properties of the species making up the entire process.

The matrix support plate 117 may, except for the apertures, be impervious to exhaust gas flow, or it may allow flow through it at other locations as well (e.g., if formed from a screen, mesh, perforated plate, or other structure pervious to flow). Optional support bars 118, or equivalent structures, may be used to help support the weight of the matrix bed 150, especially when the flameless thermal oxidizer 100 is mounted in a vertical orientation.

In operation, combustible vapor enters the flameless thermal oxidizer 100 through the inlet nozzle 110, producing a combustible vapor flow. As used herein, the term “combustible vapor” means a gas (typically air) containing a vapor of an organic compound, or containing a mist or fog of a liquid organic compound. The mixture may be above the lower flammability limit (LFL) thereof, or it may be below the LFL. It may be above the upper flammability limit (UFL), or below it. Typically, the combustible vapor will have a composition below the LFL. Vapors in the combustible vapor flow may originate from a wide variety of sources, nonlimiting examples of which may include capture of volatile organic compounds (VOC's) from any of a variety of processes, for example solvent-based coating operations.

In one embodiment of the invention, the linear flow rate of combustible vapor along the feed passage(s) 130 is close to or equal to that of the exhaust gases moving downward through the matrix bed 150. Such an arrangement may maximize heat transfer between the incoming combustible vapor and the exhaust gases, thereby increasing the fuel efficiency of the flameless thermal oxidizer 100. In one embodiment of the invention, the ratio of combustible vapor flow rate to exhaust flow rate is between about 0.9:1 and about 1.1:1. This range is typical, but it may optionally extend from 0.5:1 to 1.5:1. Typically, the gas velocities should range between about 10 feet per second and about 25 feet per second.

Flameless thermal oxidizer devices according to the invention may be capable of oxidizing combustible vapors at low levels of concentration, due to the high thermal efficiency of the devices. In may cases, no supplemental fuel is needed, and the combustible vapors themselves provide sufficient enthalpy of oxidation to keep the unit running properly. In one embodiment of the invention, the level of combustible material in the combustible vapor entering the flameless thermal oxidizer has a BTU level of less than 20 BTU/scf, and preferably less than 10 BTU/scf. Combustible vapors having a heat content as low as about 4-5 BTU/scf may be efficiently oxidized, using a supplemental fuel such as may be introduced at fuel inlets 124 shown for example in FIG. 3.

By keeping the BTU level within the feed tubes low, it may be possible to reduce the absolute amount of oxidation that occurs within the feed tubes, thereby increasing the useful life of the tubes. Fuel such as may be necessary to supplement the heat produced by the flameless oxidation of combustible vapor, in order to maintain a sufficiently high working temperature, is optionally added proximal to the outlets of the feed tubes, for example as indicated at fuel inlets 124 in FIG. 4. Or, such fuel may be added at another point downstream of the exit of feed tubes 131.

EXAMPLE

In FIG. 9, there is shown the results of a computer simulation of the temperature profile in a flameless thermal oxidizer according to one embodiment of the invention, with the results shown as a schematic illustration of calculated isotherms. FIG. 9 illustrates this temperature profile as it relates to an embodiment of a feed tube 231 and a mixing region 228 similar to region 28. The calculated isotherms predict the heat transfer flux between the feed tube wall and the matrix bed.

The map shows lines indicating temperatures T₁ to T₁₀ in relation to one side of the feed tube 231, with temperatures outside the tube indicated above the wall of the tube indicated at 231 and temperatures inside the tube 231 indicated below the wall. Mixing region 228 is indicated in the area proximal to the end of feed tube 231.

The simulation illustrated in FIG. 9 is based upon the parameters is defined in the following table: Parameter Value Feed Species Methane-Air Mixture: 0.011 wf CH₄, 0.2304 wf O₂ Feed Tube Material Stainless Steel Grade 310 Vessel Insulation Refractory: C_(p) = 856 j/kg-k, k = 0.5 w/m-k, density = 2960 kg/m³ Inlet Velocity 3.05 m/sec (10 ft/sec) Pressure Atmospheric wf = weight fraction

As a result of a simulation based on the foregoing parameters, the temperature profiles illustrated in FIG. 9 were developed. Specifically, the temperatures shown in the following table resulted from the simulation: T₁ 1104° F. T₂ 1168° F. T₃ 1232° F. T₄ 1360° F. T₅ 1424° F. T₆ 1488° F. T₇ 1616° F. T₈ 1744° F. T₉ 1872° F. T₁₀ 1936° F.

Although the invention is illustrated and described herein with reference to specific embodiments, the invention is not intended to be limited to the details shown. Rather, various modifications may be made in the details within the scope and range of equivalents of the claims without departing from the invention. 

1. A gas recuperative flameless thermal oxidizer comprising: a matrix bed; and at least one feed passage extending at least partially within said matrix bed, said feed passage having an inlet configured to receive combustible vapor or an air-combustible vapor mixture and an outlet configured to deliver the combustible vapor or the air-combustible vapor mixture into said matrix bed, said at least one feed passage having a cross-sectional area and a length within the matrix bed, wherein a ratio of said length (ft) to said cross-sectional area (in²) is at least about 0.5:1.
 2. The gas recuperative flameless thermal oxidizer of claim 1, wherein said ratio of said length (ft) to said cross-sectional area (in²) is from about 0.5:1 to about 2.5:1.
 3. The gas recuperative flameless thermal oxidizer of claim 1, wherein said cross-sectional area of said at least one feed passage is about 29 in² or less.
 4. The gas recuperative flameless thermal oxidizer of claim 1, wherein a cross sectional area defined by the at least one feed passage, taken together, is between about 10% and 50% relative to a cross sectional area of the matrix bed.
 5. The gas recuperative flameless thermal oxidizer of claim 1, wherein a cross sectional area defined by the at least one feed passage, taken together, is between about 20% and 30% relative to a cross sectional area of the matrix bed.
 6. The gas recuperative flameless thermal oxidizer of claim 1, wherein said length of said feed passage is about 2 ft or more.
 7. The gas recuperative flameless thermal oxidizer of claim 1 comprising a plurality of feed passages, said feed passages being positioned at a pitch of between about one and eight inches.
 8. The gas recuperative flameless thermal oxidizer of claim 7, wherein the pitch is between about five and eight inches.
 9. A method of oxidizing combustible vapor in a gas recuperative flameless thermal oxidizer, said method comprising the steps of: delivering combustible vapor or an air-combustible vapor mixture below the lower flammability limit into an inlet of a feed passage and through an outlet of the feed passage to a matrix bed; maintaining a length within the matrix bed of the feed passage such that a ratio of the length (ft) to the cross-sectional area (in²) of the feed passage is at least about 0.5:1.
 10. A gas recuperative flameless thermal oxidizer comprising: a matrix bed; and at least one feed passage extending at least partially within said matrix bed, said feed passage having an outlet configured to deliver combustible vapor or an air-combustible vapor mixture into said matrix bed; and at least one separate fuel inlet configured to introduce fuel into said matrix bed, said fuel inlet being positioned downstream of said outlet of said feed passage.
 11. The gas recuperative flameless thermal oxidizer of claim 10, wherein the fuel inlet is positioned proximal to the outlet of the feed passage.
 12. The gas recuperative flameless thermal oxidizer of claim 10, wherein the fuel inlet is positioned co-linear with the outlet of the feed passage.
 13. A method of oxidizing combustible vapor in a gas recuperative flameless thermal oxidizer, said method comprising the steps of: delivering combustible vapor or an air-combustible vapor mixture below the lower flammability limit into a matrix bed through an outlet of a feed passage; and introducing fuel into the matrix bed through a separate fuel inlet at a position downstream of the outlet of the feed passage.
 14. The method of claim 13, wherein said introducing step comprises introducing fuel at a position proximal to the outlet of the feed passage.
 15. The method of claim 13, wherein said introducing step comprises introducing fuel at a position co-linear with the outlet of the feed passage.
 16. The method of claim 13, wherein the step of introducing fuel comprises introducing natural gas.
 17. The method of claim 13, wherein the step of introducing fuel comprises introducing No. 2 fuel oil.
 18. A gas recuperative flameless thermal oxidizer comprising: a matrix bed; and at least one feed passage extending at least partially within said matrix bed, said feed passage having an inlet configured to receive combustible vapor or an air-combustible vapor mixture and an outlet configured to deliver the combustible vapor or the air-combustible vapor mixture into said matrix bed; said feed passage defining an interior extending within the matrix, said interior being substantially devoid of matrix.
 19. A method of oxidizing combustible vapor in a gas recuperative flameless thermal oxidizer, said method comprising the steps of: delivering combustible vapor or an air-combustible vapor mixture below the lower flammability limit into an inlet of a feed passage and through an outlet of the feed passage to a matrix bed; maintaining an interior of the feed passage extending within the matrix of the feed passage substantially devoid of matrix.
 20. A gas recuperative flameless thermal oxidizer comprising: a matrix bed positioned to exhaust gaseous oxidation products along an exhaust path; and at least one feed passage extending at least partially within said matrix bed, said feed passage having an inlet configured to receive combustible vapor and an outlet configured to deliver the combustible vapor into said matrix bed, said feed passage defining a combustible vapor path extending within the matrix in a direction substantially opposite that of said exhaust path of said matrix bed; wherein said combustible vapor path of said feed passage and said exhaust path of said matrix bed are configured to provide a ratio between the velocity of combustible vapor in said combustible vapor path and the velocity of exhaust in said exhaust path between about 0.5:1 and 2.5:1.
 21. The gas recuperative flameless thermal oxidizer of claim 20, wherein the ratio between the velocity of combustible vapor in said combustible vapor path and the velocity of exhaust in said exhaust path is between about 0.9:1 and about 1.1:1.
 22. A method of oxidizing combustible vapor in a gas recuperative flameless thermal oxidizer, said method comprising the steps of: delivering combustible vapor below the lower flammability limit into an inlet of a feed passage, along a combustible vapor path, and through an outlet of the feed passage to a matrix bed; exhausting gaseous oxidation products along an exhaust path in the matrix bed in a direction that is substantially opposite that of the combustible vapor path of the feed passage; and maintaining a ratio between the velocity of combustible vapor in the combustible vapor path and the velocity of exhaust in the exhaust path between about 0.5:1 and 2.5:1.
 23. The method of claim 22, wherein said maintaining step comprises maintaining the ratio between the velocity of combustible vapor in said combustible vapor path and the velocity of exhaust in said exhaust path between about 0.9:1 and about 1.1:1.
 24. A gas recuperative flameless thermal oxidizer comprising: an enclosure; a matrix bed contained within said enclosure; feed tubes extending into said enclosure and at least partially within said matrix bed, said feed tubes being positioned to deliver combustible vapor or an air-combustible vapor mixture into said matrix bed; and a matrix bed support mounted within said enclosure, said matrix bed support having a surface substantially impervious to the flow of exhaust supporting said matrix bed, said matrix bed support defining apertures therein each sized to receive a feed tube and provide exhaust passages proximal to said apertures.
 25. In a gas recuperative flameless thermal oxidizer having an enclosure, a matrix bed contained within the enclosure, and feed tubes extending into the enclosure and at least partially within the matrix bed, a method of oxidizing combustible vapor comprising the steps of: delivering combustible vapor or an air-combustible vapor mixture below the lower flammability limit into the matrix bed through the feed tubes; directing substantially all gaseous oxidation products in the matrix bed through apertures in a matrix bed support adjatent the feed tubes; and exhausting gaseous oxidation products from the gas recuperative flameless thermal oxidizer through an outlet in the enclosure.
 26. A gas recuperative flameless thermal oxidizer comprising: an enclosure extending between opposed end portions; a matrix bed contained within said enclosure; feed tubes extending into said enclosure and at least partially within said matrix bed, said feed tubes being positioned to deliver combustible vapor or an air-combustible vapor mixture into said matrix bed; and means for adjusting the distance between said opposed end portions of said enclosure to increase or decrease the size of the matrix bed.
 27. The gas recuperative flameless thermal oxidizer of claim 26, said adjusting means comprising at least one wall section configured to be added to or removed from said enclosure between said opposed end portions of said enclosure.
 28. The gas recuperative flameless thermal oxidizer of claim 27, said wall section having a surface configured to be coupled to another wall section or to one of said opposed end portions of said enclosure.
 29. The gas recuperative flameless thermal oxidizer of claim 26, said adjusting means comprising at least one extension section configured to be added to or removed from said feed tubes between said opposed end portions of said enclosure.
 30. The gas recuperative flameless thermal oxidizer of claim 29, said extension section having a surface configured to be coupled to another extension section or to another portion of said feed tubes.
 31. The gas recuperative flameless thermal oxidizer of claim 1, wherein said ratio of said length (ft) to said cross-sectional area (in²) is at least about 1.2:1.
 32. The gas recuperative flameless thermal oxidizer of claim 31, wherein said ratio of said length (ft) to said cross-sectional area (in²) is from about 1.2:1 to about 2.1:1.
 33. The gas recuperative flameless thermal oxidizer of claim 1, wherein said ratio of said length (ft) to said cross-sectional area (in²) is about 1.6:1. 